1. Blade Runner 

Blade Runner follows policeman Rick Deckard, and the pursuit of four illegally cloned humans in a dystopian, futuristic Los Angeles. So many things make this movie the best: a brooding score, the "I've seen things..." polemic, and the iconic future LA cityscape all work to tell a gripping story.

2. 2001: A Space Odyssey 

It achieved world-wide praise for its revolutionary special effects.

It had many brilliant moments: accurate simulations of space that are still unparalleled even with today's CGI, the characterization of Hal, the malevolent super-computer, and using classical music in the opening scene.

3. Star Wars

The film weaved themes of good warring with evil in a space opera setting. It used an all-encompassing "force" wielded for good or evil, adding a touch of mysticism not usually seen in sci-fi films. It was the first blockbuster, influencing sci-fi sagas for decades thereafter.

4. Alien 

It was lauded for Gothic set design, terrifying Aliens, and heroic Ripley, played by Sigourney Weaver. Alien also addresses themes of motherhood, and shows effective tension by showing long stretches of quiet followed by scenes of sheer terror.

5. Solaris 

A compelling, tragic drama of a psychologist travelling to another planet to replace a scientist. Once he arrives, he meets secretive survivors... and his dead wife. Reality is replaced with the dreams of the planet's alien intelligence.

6. Terminator 

Robots from the future send a cyborg back in time to assassinate a future human rebel's mother. It's a perfect piece of film-making in its genre, blending gripping action with intelligent time travel mechanics.

7. The Day the Earth Stood Still 

In postwar America at the height of the Red Scare, an alien named Klaatu tries to convince the world's leaders to stop the rush towards nuclear destruction. It has excellent dramatic tension and a message of peace that was far ahead of its time.

8. War of the Worlds

HG Wells' tale of invaders from Mars of Earth was adapted into another cold war era movie. The idea that there could be life developed on different worlds which one would never recognise was a compelling idea for its time. The spare special effects only heightened the contrast between humans and the unknowable invaders. 

9. The Matrix

Stylish clothes, martial arts action, and ground-breaking special effects combined to make a fresh spin on artificial intelligence enslaving humans. It also pioneered the use of "bullet time" sequences used worldwide today.

10. Close Encounters of the Third Kind

A tale of Richard Dreyfus' growing obsession with aliens against a backdrop of a mysterious governmental agency has given the core of sci-fi film lore ever since.